The present invention relates to extrusion apparatus, and more particularly, to apparatus for extruding soft plastic materials.
In the manufacture of biscuit sandwiches, such as sandwich cookies, single biscuits are arranged in rows on a conveyor which passes under a filling-extruding cylinder. The extruding cylinder drops a slice of an extruded filling, such as an icing, onto each of the biscuits. The second biscuit is then added to complete the sandwich.
The extruding cylinders used in the past are of the type shown in U.S. Pat. No. 2,868,141. In these a solid cylinder is fitted with several circumferential rows of spaced pistons which reciprocate within radial bores that intersect the outer surface of the cylinder.
Positioned above the cylinder is a hopper containing filling material. The mouth of the hopper abuts the curved wall of the cylinder, sequentially exposing the bores to the filling material as the cylinder rotates.
The pistons, as they pass the mouth of the hopper, are retracted by a cam mechanism to draw a slug of filling into the bore. As the pistons are carried downwardly toward the conveyor, they are extended to expose the slug of filling. A taut wire slices off a section of the slug, allowing it to fall onto the biscuit.
This type of construction is expensive in that it requires many parts, some of which must be made to precise dimensions. For example, the extruding piston must fit exactly into the bore in which it slides.
Because of the complexity and precision of the mechanism, periodic cleaning of the apparatus requires expensive disassembly and is therefore expensive. Additionally, replacement of broken and worn parts becomes a significant cost facter in using such a complex arrangement.
A very significant limitation of the piston type extruder is that such a mechanism can be used only to extrude round slugs of filling. As a practical matter, a tight fit between the piston and bore can be achieved only in the manufacture of round sandwiches.
Another significant limitation of this type of extruder is that the thickness of the extruded slug cannot be changed without making extensive changes in the mechanisms.
Another type of extruding cylinder used in the past is of the type shown in U.S. Pat. No. 4,397,628. In this type of extrusion cylinder, a plurality of paddles are used inside the rotating cylinder to create channels of flow between the tilted paddles and the interior surface of the rotating cylinder. These paddles cause predetermined amounts of icing to be extruded through a die during each passage of a particular die past a particular paddle. A significant limitation of this type extruder is that such a mechanism cannot be used to extrude precisely determined weights of slugs of icing due to variations in the icings used, the temperature changed during a run of the icing, and any other factors affecting the viscosity of the icing material. Furthermore, since the setting of the paddles is a slow, trial-and-error process, it is not readily possible to instantaneously adjust the weight of slugs (proportional to the amount of icing extruded during each cycle) while the cylinder is rotating. This can be a significant limitation in instances where the biscuit weights themselves vary, since in such an instance it is very desirable to increase or decrease the weight of the icing slugs deposited upon the sandwiches to compensate for the change in weight of the biscuits. For example, where a new batch of biscuits has a somewhat lighter weight than previous biscuits, and the total weight of each sandwich is to be made constant, the amount of icing deposited cannot be increased readily and continuously in the device of this patent.